Electrical connectors



June 17, 1958' G P, FELTS ET A 2,839,595

ELECTRICAL CONNECTORS Filed Dec. l2, l9

2 Sheets-Sheet l [GORDON ,I? F T INVENTOES, Reamer WJ'H y 65%9Xh/5 H Lin/l5 TTO RNE y.

United States Patent ELECTRICAL CONNECTORS Gordon P. Felts, Sierra Madre, Robert W. Seeger, Covina,

' and Maxwell H. Lewis, Altadena, Calif., assignors, by

direct and mesne assignments, to Microdot Inc., a corporation of California Application December 12, 1952, Serial No. 325,588

11 Claims. (Cl. 174-89) This invention relates to fittings for cables, and particularly to miniature connectors for insulated and shielded cables.

While the connectors may be adapted to various size cables, it finds its particular value in connectors for cables of small diameter. Thus connectors of the type described herein have been used in shielded and insulated cables having an external diameter of about 0.1", the connectors in this particular case having a total length of A1" and a diameter of about 0.225 at its maximum diameter. These dimensions are not given as any limitation of size in which the connector is made, but to point out that by reason of the invention connectors of such small size can be formed to make electrical contact With shielded cables of even minute size.

In order to obtain such utility for the connectors of our invention we have employed a solderless connection of the various electrical components of the cable and connectors and have relied on compression and pressure fittings and joints.

As is well known, shielded cables are composed of an inner conductor, for example, a fine copper wire which is insulated by an insulating sleeve. An outer electrically conductive tubular shield, conventionally in the form of a braided wire tubing, is placed about the insulated inner jacket and an outer insulating cover is placed about the braided jacket. In order to connect this cable electrically, a connector is provided whereby the inner wires are electrically connected and the braided cover of each cable section is electrically connected but insulated from the inner wire. In connecting the cable to instruments or other electrical equipment, or other such cables, the inner wire is electrically connected in an electrical circuit, while the braided wire may be grounded but, if desired, also insulated from the electrical circuit or otherwise electrically isolated from the inner wire.

In order to obtain these functions we form our connector in two parts, a socket element and plug element. In the plug, a wire terminal element is connected to the inner wire electrically isolated from the plug by a tubular insulating sleeve. A shield terminal element is connected to the braided sleeve which is positioned around the insulating sleeve. By employing for such sleeve an insulating material of considerable elasticity, and by placing a container having a relatively rigid circumarnbient wall about the braided material and employing as the inner wire terminal a wedge-shaped member, a Wedge action is created so as to compress, radially, the tubular insulating sleeve. The wire is pressed against its terminal element and the tubular element simultaneously presses the braided shield radially against the rigid container, making a solderless and sure electrical connection between the braided shield and its terminal and between the Wire and its terminal.

As another feature of the invention a socket is provided to receive the plug. The socket is electrically isolated from the circumambient wall of the fitting holding the socket.

These and other objects of the invention will be further described in connection with the drawings, in which:

Fig. l is a vertical section through the socket element of the fitting;

Fig. 2 is a vertical section, with parts in elevation and parts in section and parts broken away, showing the housing element of the socket and with the socket sleeve and cable in position prior to entry into the socket element;

Fig. 3 is an exploded view in section of the socket element;

Fig. 4 is a vertical section through the assembled connector and cable;

Fig. 5 is a section taken on the line 5-5 of Fig. 4;

Fig. 6 is a section taken on the line 6-6 of Fig. 4;

Fig. 7 is a fragmentary section showing a modification of the plug; and

Fig. 8 is a partial vertical section of a modification of the connector of this invention.

The connector is composed of a socket element 1 and a plug element 2. The plug is formed of a hollow tubular ferrule 3 and slotted in a series of vertical slots 5 extending at spaced points around the circumference of the lower end 4 of the ferrule. The ferrule carries an internal flange 6 at an intermediate portion of the ferrule providing a bore of somewhat less diameter than the bore 6' of the ferrule. Also the ferrule carries a flange 6 at the upper end of the ferrule.

The ferrule bore 6' is grooved at its upper end with a conical groove 7 which terminates at an internal shoulder 8 which has an internal bore 9 of the same diameter as the bore of the ferrule. The internal flange 6 formed above the slit end 4, provides an internal shoulder 6 An external circumferential groove is positioned at 9' on the ferrule 3 and a snap ring 10 is positioned in the groove for the purpose to be described below.

A nut 11 having an internal flange 12 and threaded at 13 is passed over the ferrule. The internal surface 13' of the flange 12 abuts against the lower surface 14 of the flange 6. If room is present an O-ring 13 or equivalent gasket may be set on the surface 13' (as shown in Fig. 7) to improve the seal between the shoulder 12 and the flange 6.

To mount the cable in the plug there is provided an insulating resilient tubular sleeve 15. When the connector is connected to the cable, the cable is first passed through the bore 6" of the ferrule and 6 of the flange. The outer insulation 16 is stripped back to expose a length of braided wire shield over which the ferrule is passed, the braided wire passing through the bore 6 and the internal flange 6 The conductor wire 19 is bared for a short section beyond the end of inner insulation 18 and the braided shield 7 is separated from the insulation 18 so that the insulating bearing 15 may be slipped over the inner insulation 18 and inside the braided wire 17 with exposed end of the wire 19 just inside the end of the insulating sleeve 15', as shown in Fig. 2. The braided wire and the insulating sleeve are then drawn inside the ferrule through the bore of 9 and into the bore 6' until the top of the sleeve 15 is about flush with the top of the flange 6. The inner flange 6 acts as a limit motion stop.

As will be seen from Fig. 4, the braided sleeve is between the insulating sleeve and the wall of the ferrule 3. The outer insulation 16 is pushed up into the ferrule until the upper end of the outer insulation 16 abuts against the lower surface of the flange 6 (see Fig. 4). The slit end 4 of the ferrule is then compressed to clamp the slit end 5 against the outer insulation to compress the wire and insulation 16 in place in the ferrule.

, After the cable is in place in the ferrule and the sleeve has been entered, as described above, the wedge pin 21 is introduced, as described below. I

The wedge plug pin 20 has one end 21 pointed and carries a series of conical serrations 22 in the form of truncated cones 24 having at the base of the cone an annular shoulder 25. The lower end of the pin 20 is in the form of the apex 26 of the terminal cone 27.

The pin 20 is driven into place by inserting the apex 26 between the wire 19 and its insulating sheath 18. The cones wedge the inner insulation 18 apart and also press the insulating sleeve 15 apart, wedging its upper surface into the'conical slot 7 (see Fig. 4) and pressing the pin 20 against the wire to make a sure electrical connection between the wire 19 and the wedge pin 26 The wedge pin is inserted so that the upper annular shoulder of the uppermost truncated cone 22 is just below the top of the sleeve 15, the pin extending beyond the upper surface of the sleeve and out of the ferrule. It will be observed that the pin 2% is secured against displacement out of the sleeve 15 by reason of the serrations which bite into the sleeve 15 and resist displacement. It will also be observed that the sleeve 15 is secured against displacement out of the ferrule both by the flange 6 and also 'by the fact that the upper end is wedged underneath the flange 8 and inside the conical groove 7. The metallic electrically conducting ferrule thus acts as a tubular container for the insulating sleeve. The cable and the plug pin are thus securely held in place in the ferrule.

The socket element is formed of stud 28 having an internal bore 29. The upper end of the bore 29 is reduced in a conical neck 30 and a conical groove 32 is formed at the other end of the stud and forms an internal shoulder 31 at the base of the conical groove. A flange 33 is placed intermediate the ends of the stud 28 and is formed at the outer periphery of the flange so as to receive a wrench to turn or hold the stud when desired. The stud 28 is threaded at 33 and 34 at each end of the stud and on each side of the flange 33. The insulating sleeve 35, having an outer diameter somewhat greater than the diameter of the bore 29, is compressed and shoved into the bore 29 until its end 36 is flush with the end of the stud 28 with the adjacent end compressed in the conical neck 30. The other end 37 is expanded by its resilience into the conical groove 32. Positioned inside the bore 28' is an electrically conductive metallic tube 39 with its end 41 extending beyond the end 36 and the end 42 extending beyond the other end of the sleeve 35. The end 42 is slit at 43 and the tube carries external serrations 44. It will be seen that the sleeve is compressed inside the bore 29 with its upper end 36 wedged inside the conical neck 30 and its lower end wedged inside the conical groove 32 underneath the flange 31. The tube 39 is held in position by the serrations 44 which cut into the insulating sleeve 35.

To assemble the plug and socket (see Fig. 4), the nut 11 is dropped until it is stopped by the retaining ring 10, as indicated by dotted lines in Fig. 2, exposing the pin 20. An O-n'ng 41' is placed over the threaded end 34. The pin 20 is entered into the bore at the slit end 42. The bore 40 is of such diameter that the pin 20 makes a friction fit inside the bore 40, thus making a good electrical contact between the pin 20 and the tubular socket 39. The nut 11 is screwed upon the end 34 to compress the O-ring 41'. A contact washer 42 is slipped over the threaded end 33 and held in place by means of the lock nut 43.

. It will be seen that the connector is made weather-tight by means of the O-ring 41' and the press fit of the insulating bushingatthe end 36 aided, if desired, by the O-ring 13 The ground may, as will be understood, be connected to the washer 42', thus grounding the braided shield sleeve, via the metallic nut 11, the metallic ferrule 3 and stud 28, and an electrical connection can be made to the etallic tube 39 at the end 41.

If desired, however, as shown in Fig. 8, the end 41 may be formed in the same manner as the end 42 and by making the threaded end 33 the same as 34 and removing the lock nut 43 a plug fitting identical to that described above may be entered into the upper end and the nut 11 thereof screwed against an additional O-ring or washer 41' in the same manner as illustrated in Fig. 4, thus making it possible to connect two lengths of cable and to connect the braided sheath to ground.

While various electrical insulating materials may be employed for forming the sleeves 15 and 36, we have found that Teflon, a polymerized tetrafluoroethylene made by polymerization of tetrafluoroethylene, and sold by the Du Pont de Nemours Company, of Wilmington, Delaware, is suitable. Such materials are particularly suitable for our purposes since they have an operating range of from a very low to a relatively high temperature and are good electrical insulators. They are resistant to moisture, can be molded, machined, and drilled to close tolerances. Other resilient materials which will have high electrical resistance and may be fashioned into tubular form may also be employed.

While we have described a particular embodiment of our invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

We claim:

1. A plug connector element for cables comprising an outer tubular container, a first inner insulating sleeve, a conductive wire extending into the tubular container, a

- second insulating sleeve positioned in said container within said first sleeve, a conductive braided shield positioned about said sleeves and in electrical contact with said outer container, a pin positioned in said sleeves and protruding outside said first sleeve, the end ofsaid pin being positioned in one end of said last-named conductive braided shield and making an electrical pressure contact with said wire inside said sleeves, said wire being disposed between said pin and said sleeves.

2. A plug connector element for shielded cables, said cable comprising an inner electrical wire, an insulation for said wire, an outer conductive tubular conduit about said insulation, said connector element comprising an electrical conductive tubular container, an insulating sleeve positioned in said tubular container, one end of said Wire being positioned within said sleeve, one end of said conductive tubular conduit positioned between the outer wall of said sleeve and the inner wall of the container, a wedge pin, one end of said pin positioned within the sleeve and in electrical contact with said wire in said sleeve, and the other end of said pin protruding beyond the end of said sleeve, said wire being wedged between said pin and said sleeve, and said pin forcing said conductive tubular conduit radially against said tubular container.

3. A plug connector element for an electrical conduit comprising a tubular ferrule, an inner flange at one end of said ferrule, a conical groove in the wall of said ferrule, the inner surface of said flange forming an internal shoulder at the base of said conical groove, a bore through said ferrule, a resilient insulating sleeve, an inner bore for said sleeve, said sleeve having a normal outer diameter greater than the inner diameter of said ferrule and fitting in said ferrule under compression, one end of said sleeve fitting inside the conical groove and abutv ting against said inner shoulder, a conductive wire inside side the inner bore of said sleeve, said conductive wire positioned between said wedge pin and the inner wall of said sleeve, said pin extending beyond the end of said sleeve and ferrule.

4. A solderless plug connector element for an electrical shielded cable, said cable including an inner conductive wire, an insulating cover for said wire, a braided wire shield surrounding said insulating cover, said element comprising a tubular ferrule, a bore through said ferrule, a resilient insulating sleeve, an inner bore for said sleeve, said sleeve having a normal outer diameter greater than the inner diameter of said ferrule and fitting in said ferrule under compression, an electrical conductive wire inside the inner bore of said sleeve, said braided shield positioned between the inner wall of said ferrule and the outer Wall of said sleeve, a wedge-shaped pin positioned inside the inner bore of said sleeve, said wire positioned between said wedge pin and the inner wall of said sleeve, said pin extending beyond an end of said sleeve and ferrule.

5. A solderless plug connector element for an electrical shielded cable, said cable including an inner conductive wire, an insulating cover for said wire, a braided wire shield surrounding said insulating cover, said connector element comprising a tubular ferrule, a bore through said ferrule, an inner flange at one end of said ferrule, a conical groove in the Wall of said ferrule, the inner surface of said flange forming an internal shoulder at the base of said conical groove, a resilient insulating sleeve, an inner bore for said sleeve, said sleeve having a normal outer diameter greater than the inner diameter of said ferrule and fitting in said ferrule under compression, one end of said sleeve fitting inside the conical groove and abutting against said inner shoulder, an elec trical conductive wire inside the inner bore of said sleeve, said braided shield positioned between the inner wall of said fererule and the outer wall of said sleeve, a Wedgeshaped pin positioned inside the inner bore of said sleeve, said wire positioned between said wedge pin and the inner wall of said sleeve, said pin extending beyond an end of said sleeve and ferrule.

6. In combination, a plug connector element for cables and a socket connector element, said plug connector element comprising an outer conductive container, an inner insulating sleeve, an electrically conductive wire positioned in said sleeve, a pin positioned in said sleeve and protruding outside said sleeve, said pin being in electrical contact with said Wire, the end of said wire being disposed between said pin and said sleeve, a conductive braided shield positioned about said sleeve and in contact with said outer container, said pin placing said sleeve and said braided shield in compression against said container; said socket connector element including a conductive stud having an internal bore, an insulating sleeve positioned in said bore, an electrically conductive tube positioned in said sleeve, the end of said pin protruding from said first-mentioned sleeve being positioned in one end of and in electrical contact with said last-named electrically conductive tube, and electrically conductive means for connecting the outer container and the stud of said plug and socket connector elements, whereby said braided shield is electrically connected to said conductive stud.

7. In combination, a plug connector element for an electrical conduit and a socket connector, said plug connector element comprising a tubular conductive ferrule, an inner flange at one end of said ferrule, a conical groove in the wall of said ferrule, the inner surface of said flange forming an internal shoulder at the base of said conical groove, a bore through said ferrule, a resilient insulating sleeve, an inner bore for said sleeve, said sleeve having a normal outer diameter greater than the inner diameter of said ferrule and fitting in said ferrule under compression, one end of said sleeve fitting inside the conical groove and abutting against said inner shoulder, a conductive wire inside the inner bore of said sleeve, a wedge pin positioned inside the inner bore of said sleeve, said conductive wire positioned between said wedge pin and the inner Wall of said sleeve, said pin extending beyond the end of said sleeve and ferrule, a conductive braided shield positioned about said sleeve and in contact with said ferrule; said socket connector including a conductive stud having an internal bore, an insulating sleeve positioned in said bore, an electrical conductive tube positioned in said sleeve, the end of said pin extending beyond said first-mentioned sleeve being positioned by a friction fit in one end of said last-named conductive tube, and electrically conductive means for connecting said ferrule and said stud of said plug and socket fitting.

8. A plug connector element as defined in claim 3, wherein said wedge pin carries a plurality of conical serrations in the form of truncated cones.

9. A socket connector element comprising an outer tubular container, a conical neck at one end of said container, an outwardly extending conical groove at the other end of said container, an internal shoulder on said container adjacent the outer end of said groove, a resilient electrical insulating sleeve positioned within said container, said sleeve having an outer diameter somewhat greater than the diameter of the bore of said container, said sleeve being compressed into said neck and expanded into said groove, one end of said sleeve abutting against said shoulder, and a conductive tube positioned in said sleeve.

10. A connector element comprising an outer tubular member, a conical neck at one end of said member, an outwardly extending conical groove at the other end of said member, an internal shoulder on said member adjacent the outer end of said groove, a resilient electrical insulating sleeve positioned Within said member, said sleeve having an outer diameter somewhat greater than the diameter of the bore of said member, said sleeve being compressed into said neck and expanded into said groove, one end of said sleeve abutting against said shoulder, and a conductive element positioned in said sleeve.

11. A socket connector element comprising a stud having a cylindro-conical bore, said bore having a cylindrical central surface portion and conical surface portions at each end of said cylindrical surface portion, a resilient electrical insulating sleeve positioned in said bore adjacent said cylindrical and conical surface portions of said bore, said sleeve having a normal outer diameter somewhat greater than the diameter of said bore at the cylindrical surface portion, said sleeve being compressed against said cylindrical and conical surface portions, and an electrically conductive tube positioned in the bore of said sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 

